In a recent $5-$year period, mutual fund manager Diana Sauros produced the following percentage rates of return for the Mesozoic Fund. Rates of return on the market index are given for comparison.

$12345$

Fund $1\mathrm{.}2+24\mathrm{.}8+40\mathrm{.}7+11\mathrm{.}1+0\mathrm{.}3$

Market index $0\mathrm{.}9+16\mathrm{.}0+31\mathrm{.}7+10\mathrm{.}90\mathrm{.}7$

Calculate the standard deviation of the market index. Answer in percentages with $2$ decimal points.